Convenient characterization of polymers grafted on cellulose nanocrystals via SI-ATRP without chain cleavage

Cleaving is usually required to characterize the molecular weight of grafted polymers on substrates. Here, we report on a technique to estimate the molecular weight of grafted polystyrene (PS) (M-n(grafted) (PS)) in PS-grafted cellulose nanocrystals (PS-g-CNCs) without chain cleavage. PS-g-CNCs were prepared from brominated CNC (CNC-Br) by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) in the presence of sacrificial initiators. Differential scanning calorimetry (DSC), dynamic light scattering (DLS), and thermogravimetric analysis (TGA) of PS-g-CNCs revealed that M-n(grafted) (PS) increased proportionally with monomer conversion. By comparing the mass of grafted PS, deduced from TGA curves, with initiating sites on CNC-Br, M-n(grafted PS) was calculated. The resultant M-n(grafted PS) was the same as M-n of free PS initiated by sacrificial initiators and matched theoretical values calculated according to monomer conversion. Therefore, grafting polymerization from CNC-Br and free polymerization were progressing in a controlled manner with the same propagating rates.